In a traditional armature circuit in a battery type electric tool, as shown in FIG. 1 which shows a schematic diagram of the traditional armature circuit in the battery type electric tool, R1 and R2 in the figure are internal resistances of high-power transistors at both ends of a motor armature; R1=R2, and R1+R2=2R1; R3 is a contact resistance of a switch; R4 and R5 are the contact resistances of a positive electrode socket and a negative electrode socket for batteries; R4=R5, and R4+R5=2R4, so the total resistance of the armature circuit (exclusive of the resistance of a motor) Rtotal=R1+R2+R3+R4+R5=2R1+R3+2R4; and it can be seen that switch contact points, battery socket contact points and other internal resistances are connected in series, so the total internal resistance is large, and current loss is excessive, causing low efficiency of the tool.
Since the advent of the battery type electric tool, the motor is always connected with the switch contact points and elastic connection contact points for connecting battery packs in series. With the technical development of a tool motor and the technical development of a lithium battery as a tool power source in recent years, the power of the battery type electric tool is also developed. Due to the operating characteristics of low voltage and high current of the battery type electric tool, the contact resistances of external parts in the armature circuit of the tool motor become obstacles to expansion of tool power. The characteristic is that a rotating speed is apparently decreased with the increase of a motor load (current is increased), i.e., operating efficiency is decreased. In one operating cycle of the electric tool, e.g., drilling of holes in a board, with the decrease of the rotating speed, the time for the operating cycle is also prolonged, and power consumption is also increased for battery energy, so battery use efficiency is decreased. Meanwhile, temperature rise of each contact point part is increased to bring about unsafe factors.
Thus, an invention patent Switching Device of Shanghai Baicheng Electric Equipment Manufacture Co., Ltd. exists in the industry, to effectively use a multi-contact technology, and to overcome technical difficulties of German “Marquardt” Company which monopolizes a high-power switching technology for decades in the world. The core of the technology is to reduce the internal resistance of the switch, but the internal resistance cannot be eliminated. Meanwhile, international top electric tool brands, such as “Milwaukee” and “DeWalt” in the United States, “Bosch” in Germany, and “MaKita” in Japan, also start to develop single-piece elastic connection into double-sided elastic connection with respect to connection of battery packs of products since 2012; and a contact end is divided into two end surfaces, to form double-sided two points, with a total of four contact points, i.e., four contact resistances are connected in parallel. Two brands, “Milwaukee” and “DeWalt”, belong to two companies in the United States, and dominate the high-end market of global battery type electric tools.
Even so, the above-mentioned existing art still does not change a traditional structure that the armature circuit is connected with the switch contact points and elastic static contact points of battery pack clips in series. Operating characteristics of hardness and the operating efficiency of the battery type electric tool and the energy efficiency of the battery still need to be improved.